A non-canonical ESCRT pathway, including histidine domain phosphotyrosine phosphatase (HD-PTP), is used for down-regulation of virally ubiquitinated MHC class I.
A non-canonical ESCRT pathway, including histidine domain phosphotyrosine phosphatase (HD-PTP), is used for down-regulation of virally ubiquitinated MHC class I.
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DOI：
10.1042/bj20150336
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发表时间：
2015-10-01
期刊：
影响因子：
--
通讯作者：
Luzio JP
中科院分区：
文献类型：
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作者：
Parkinson MD;Piper SC;Bright NA;Evans JL;Boname JM;Bowers K;Lehner PJ;Luzio JP
使用RNAi，确定了转运所需的内体分选复合物的非经典途径，其负责在从细胞表面下调该蛋白质期间将病毒泛素化的MHC I类分选成多泡体（MVB）。卡波西肉瘤相关疱疹病毒（KSHV）K3病毒基因产物有效下调细胞表面MHC I类。K3是一种E3泛素连接酶，可促进Lys 63连接的MHC I类多泛素化，为网格蛋白介导的内吞作用提供信号。内吞作用之后是分选成多泡体（MVB）的腔内囊泡（ILV）并最终递送至溶酶体。将MHC I类分选成MVB需要转运所需的四种内体分选复合物（ESCRT）的许多单个蛋白。在表达KSHV K3泛素连接酶的HeLa细胞中，RNAi介导的ESCRT-0和ESCRT-I复合物和三种ESCRT-III蛋白的单个蛋白质的消耗的效果表明，这些是下调MHC I类所必需的。然而，ESCRT-II复合物或ESCRT-III蛋白VPS 20（空泡蛋白分选20）/CHMP 6（带电的MVB蛋白6）的蛋白的消耗未能防止MHC I类从细胞表面的损失。组氨酸结构域磷酸酪氨酸磷酸酶（HD-PTP）的耗竭导致表达KSHV K3泛素连接酶的HeLa细胞中I类MHC的细胞表面浓度增加。用野生型（WT）和突变体HD-PTP的拯救实验支持以下结论：HD-PTP作为ESCRT-II的替代物，VPS 20/CHMP 6作为ESCRT-I和ILV形成所必需的那些ESCRT-III蛋白之间的连接。因此，下调细胞表面MHC I类，多泛素化的KSHV K3泛素连接酶，不采用经典的ESCRT途径，而是利用替代途径，其中HD-PTP取代ESCRT-II和VPS 20/CHMP 6。
Using RNAi, a non-canonical pathway of endosomal sorting complexes required for transport was identified that is responsible for sorting virally ubiquitinated MHC class I into multivesicular bodies (MVBs) during down-regulation of this protein from the cell surface. The Kaposi's sarcoma-associated herpes virus (KSHV) K3 viral gene product effectively down-regulates cell surface MHC class I. K3 is an E3 ubiquitin ligase that promotes Lys63-linked polyubiquitination of MHC class I, providing the signal for clathrin-mediated endocytosis. Endocytosis is followed by sorting into the intralumenal vesicles (ILVs) of multivesicular bodies (MVBs) and eventual delivery to lysosomes. The sorting of MHC class I into MVBs requires many individual proteins of the four endosomal sorting complexes required for transport (ESCRTs). In HeLa cells expressing the KSHV K3 ubiquitin ligase, the effect of RNAi-mediated depletion of individual proteins of the ESCRT-0 and ESCRT-I complexes and three ESCRT-III proteins showed that these are required to down-regulate MHC class I. However, depletion of proteins of the ESCRT-II complex or of the ESCRT-III protein, VPS20 (vacuolar protein sorting 20)/CHMP6 (charged MVB protein 6), failed to prevent the loss of MHC class I from the cell surface. Depletion of histidine domain phosphotyrosine phosphatase (HD-PTP) resulted in an increase in the cell surface concentration of MHC class I in HeLa cells expressing the KSHV K3 ubiquitin ligase. Rescue experiments with wild–type (WT) and mutant HD-PTP supported the conclusion that HD-PTP acts as an alternative to ESCRT-II and VPS20/CHMP6 as a link between the ESCRT-I and those ESCRT-III protein(s) necessary for ILV formation. Thus, the down-regulation of cell surface MHC class I, polyubiquitinated by the KSHV K3 ubiquitin ligase, does not employ the canonical ESCRT pathway, but instead utilizes an alternative pathway in which HD-PTP replaces ESCRT-II and VPS20/CHMP6.